Estimation of thermal properties using only one surface by means of infrared thermography

Abstract In this work was used infrared imagery to estimate thermal properties of solid materials. The Two Superficial Hot Points Technique (TSHP) was proposed and it uses heat flux and temperatures measured from a single surface of the sample to estimate the thermal diffusivity and conductivity of the material. By definition, the two parameters to be estimated are correlated and for this reason the gain ratio function concept was used to nullify this correlation, creating two independent objective functions, one for each parameter to be estimated. The gain ratio concept was extended to a three-dimensional semi-infinite model and the surface temperature was measured with infrared thermography. Associated with infrared thermography, the use of a semi-infinite mathematical model creates versatility and the possibility of estimating the properties by assessing only the region where the heat flux was applied. In other words, the geometric and boundary conditions of the sample do not need to be considered in the thermal properties estimation. The TSHP technique takes less than four minutes for temperature monitoring, it is non-destructive and uses only superficial measurements allowing, perhaps, countless in situ applications. In the present work, the thermal properties of a pipe made of Polyvinyl Chloride (PVC) were successfully estimated. In addition, a silicone rubber and copper sample were also tested. The results obtained are in good agreement with the results reported in the literature.